The present invention relates to a method for designing a turbine, in particular a low-pressure turbine, a gas turbine, in particular of an aircraft engine, a computer program product for implementing the method, and a correspondingly designed turbine.
Known from our own European Patent EP 1 738 061 B1 and our own parallel U.S. Pat. No. 7,806,651 B2, to which supplemental reference is made and the content of which is explicitly incorporated in full in the present disclosure, is a method for designing a turbine according to the preamble of claim 1 or a turbine according to the preamble of claim 11.
This European Patent proposes the design of upstream stages up to stage B1/V5 of the turbine such that a vane-to-blade ratio characteristic quantity, which indicates the ratio of the number of guide vanes to the number of rotating blades within the stage, lies between a lower cut-off limit for the mode k=−1 of the blade-passing frequency of this stage and an upper cut-off limit for the mode k=−2 of the blade-passing frequency of this stage in noise-critical operating conditions of the turbine, so as to reduce the noise level emitted from the turbine.